1. Field of the Invention
The instant disclosure relates to an Ethernet network system; in particular, to a method for cancelling common mode signal used in an Ethernet network system.
2. Description of Related Art
The HDMI Ethernet and Audio return Channel (HEAC) are brought to the latest HDMI 4.1 such that the network data signals of the HDMI Ethernet Channel (HEC) and the audio information signals of the Audio Return Channel (ARC) could be transmitted via the HDMI, so as to reduce the complexity of the household network layout lines and to provide single layout line with a great bandwidth and a high quality to transmit complete images and audios and to carry out the Ethernet transmission and the integrated applications of the network multimedia.
With well developed technology, the Internet is applied in more and more aspects. Considering that the required bandwidth of the Internet is increasing, the speed of data packet transmission of the Ethernet which is generally used has been raised from 10/100 Mbps up to over 1 Gbps. Take a common Gigabit Ethernet device for example. In the Gigabit Ethernet device with 1 Gbps transmission speed, each port has four channels. Each channel has a transceiver which communicates with other network devices via a transmission medium such as the twisted pair cable. Each transmission module usually has a transmission terminal and a receiving terminal The transmission terminal processes data and transmits data via a transmission medium to another remote network device, and the receiving terminal receives and processes data transmitted via the transmission medium. According to the standard of the Gigabit Ethernet, each device uses four channels to communicate with other network devices at the time. In other words, the Gigabit Ethernet is a full-duplex communication system.
However, in the prior art, the Ethernet network system transmits data to another remote network device via a transmission medium, and the data are usually transmitted via four channels at the same time. Thus, the working of the inner circuit or the clock generator results in common mode signals, which further generates noises in the differential mode signals and then dramatically decreases the performance and the quality of the network information signals transmitted via Ethernet network channels of the HDMI.